Aspiring jihadists looking to join the Islamic State army are often lured to the front lines with promises of changing the course of history and reclaiming a lost Islamic empire.

But at least for the less-skilled foreign recruits, the experience of fighting for the new caliphate is often brief and bloody. Kurdish and Iraqi commanders on the front lines of the war whom I interviewed in the last two weeks say that the suicide bombers and first-wave attackers deployed in Islamic State offensives are almost entirely made up of units of foreign fighters. These highly risky missions mean that the new "immigrants" fighting the infidels end up as cannon fodder, while the more prestigious organizational jobs and less-risky defensive assignments go to Syrian and Iraqi Arabs.

"The ones actively fighting in the first wave of the attacks, they are mostly using central Asian members," said Masrour Barzani, chancellor of the Kurdistan Region Security Council, who oversees much of the day-to-day fighting against the Islamic State. "Local Arab forces are used to shore up defensive positions."

General Ali al-Wazir Shamary of the Iraqi army said he had a similar experience in his battles against Islamic State forces in Diyalla Province. "We often see the foreign fighters in the first wave of attacks and then the Arab fighters will come in after an area is cleared," he said.

Some of this has already been described in social media. A Twitter account known as @wikibaghdady, thought to be a whistle-blower with knowledge of the Islamic State's internal operations, said in a series of tweets last summer that foreign volunteers would primarily be used for martyrdom operations.

This information on the order of battle is important, because U.S. intelligence agencies for nearly two years have worried that Western passport-holders who travel to Syria and now Iraq to fight with the Islamic State and al-Qaeda's affiliates could return to their home countries, battle-hardened and undetected.

Thomas Joscelyn, a senior fellow and counter-terrorism expert at the Foundation for Defense of Democracies, told me that while it's true many of the Islamic State volunteers won't survive, those that do will pose a particular threat down the line.

"The overwhelming majority of foreign fighters will not return home to commit terrorist attacks," Joscelyn said. "But some of them will. The real risk is that as the number of foreign fighters increases, the talent pool from which terrorist organizations can draw deepens. This increases the chance that terrorist groups will find highly skilled, intelligent and committed fighters who can be repurposed for plots in their home countries."

The process for recruiting foreign volunteers is very structured. Hisham al-Hashemi, a former Salafist from Iraq who is now a consultant for Iraq's Ministry of Defense and some Western intelligence agencies, told me that Islamic State recruiters will examine whether a recruit has special skills such as computer engineering or whether he is more suited for combat. After the initial vetting, the recruit will be funneled into a specific job.

Al-Hashemi said the process was akin to brainwashing. "They will give them new names and make them swear an oath of allegiance," he said. "For the foreign fighters, they will be sent to a safe house before being deployed as a suicide bomber or fighter, and they won't even know where they are or anyone else near them."

This recruitment process is detailed and well-documented. Captured records from a 2007 U.S. raid on the town of Sinjar by the Islamic State's predecessor, al-Qaeda in Iraq, show that the group kept precise documentation on their foreign volunteers. Back then, most of the foreign fighters were fellow Arabs from Libya, Saudi Arabia and Syria. There was also concern that enlisting too many foreign fighters would detract from the group's efforts to appeal to local Iraqis.

Today that pool of foreign fighters has expanded to regions including Europe, North America, Central Asia and even China. Barzani said his Peshmerga fighters have encountered Chechens, Uzbeks, Kazakhs and Turks in initial assaults. Al-Shamary told me his troops have fought Uighers, a Muslim minority group residing in western China.

"Foreigners joining the fight in Syria and Iraq are being deployed to the front-lines for a variety of purposes," said Michael Smith of Kronos Advisory, a counter-terrorism consulting firm that tracks online propaganda from jihadist groups. One, he said, it is to prove that they are not working for a foreign intelligence organization or a rival jihadist group.

But using foreign volunteers in first wave or as suicide bombers is also useful for propaganda. "Sending jihadis from the U.S., Canada, Europe or Chechnya off to meet their maker is much less likely to have the effect of degrading the group's capacity to cultivate goodwill among local populations, which the group wants to govern," Smith said. Also, advertising that recruits from all over the world are willing to die for the caliphate can encourage more volunteers.

It's been working so far. But sooner or later, the pool of potential recruits may notice that the Islamic State's volunteers don't live long enough to enjoy the new Islamic empire.

This column does not necessarily reflect the opinion of Bloomberg View's editorial board or Bloomberg LP, its owners and investors.

To continue reading this article you must be a Bloomberg Professional Service Subscriber.